Method of preparing hog cholera vaccine



Patented at. s, 1945 UNITED STATES, PATENT OFFICE luc'rnon or ranrlgirlinoc cnoLEiu 7 successors in oflice No Drawing. Application June1, 1943-, Serial No. 489,265

3 Claims. (Cl. 167-80) (Granted under the act oi March 3, 1883, as'

amended April 30, 1928; 370 0. G. 757) This application is made underthe act of March 3, 1883, as amended by the act of April 80, 1928, andthe invention herein described, if patented, may be manufactured andused by or for the Government of the United States of America forgovernmental purposes without the payment to me of any royalty thereon.

This invention relates to vaccines and a process for their preparation,with particular reference to a vaccine for immunizing swine against hogcholera.

The vaccine of this invention is prepared by using blood virus, that is,the virus in the blood of an animal infected with the disease. Suchblood virus may be obtained by using either defibrinated blood or theclear blood serum.

In preparing the vaccine, it is essential that the blood virus be sotreated that its power to produce the disease, that is, itsdisease-producing principle, is attenuated or destroyed, while its powerto stimulate the production of anti-bodies in the animal organism, thatis, its protective principle, is left comparatively unimpaired. Inaddition to this, if a vaccine is to be comparative- 1y safe to use,stable against change during storage, and safe against contaminationfrom outside sources while handled prior to injecting healthy animals,it should be so treated as to be sterile.

contaminating organisms in the vaccine may be present from afnumber ofsources. They are frequently present in the blood itself taken from thecholera-infected hog, and they may beintroduced from outside sourceswhile preparing the vaccine or through careless or unskillful handlingby persons administering it.

Such contaminating organisms may be harm! ful to a healthy animalinjected with the vaccine, and they are frequently destructive of thevaccine itself, causing spoilage of the various types. Unsterilevaccines have often failed, when not used fresh, due to destruction oftheir anti-body producing properties. Therefore, it is desirable so totreat the vaccine as to destroy contaminating organisms.

The patent to Dorset, No. 2,102,235, on whichusingtheprocessoftheDorsetpatent,ithasbeen found that a sterile vaccineis not consistently produced, due, probably to ineffectiveness of the'benzophenol to sterilize against all types of con- 1 taminatlngorganisms. Furthermore, the use of benzophenol has a detrimental effect,in that the vaccine is undesirably thickened during the attenuation orincubation stage of its production. This invention has for its objectthe production of a blood virus vaccine which is more consistentlysterile, whether contaminating organisms be present in the blood fromwhich the vaccine is derived or be introduced in the process of inakingthe vaccine or subsequent to its producion.

I have found that mixing hog cholera blood virus with an antiseptic andattenuating agent comprising crystal violet dissolved in glycerol inproper proportions, and incubating the mixture inthe conventionalmanner, results in a vaccine which is consistently sterile.

In practicing the invention, in general, crystal violet is dissolved inglycerol in the amount of about 0.25 per cent of crystal violet. Thispercentage may be varied somewhat, but over-concentration results indiillculty in eflecting the solution. This solution is then mixed withthe blood virus in the ratio of about from 15 percent to 25 percent ofsolution to about 85 percent to percent of blood virus, the optimumratio being about 20 percent of solution to percent of,

blood virus, and the mixture is then incubated in the regular'manner. Inthe selection of an antiseptic agent, it is essential that one be chosenwhich does not destroy the immunizing properties of the vaccine, whichdoes not interfere with its physical properties, and which is notharmful to the animal to be injected with the vaccine. Glycerol, whenused in the manner set forth, satisfles these conditions. 4

The following example exhibits a specific illustration of the invention.

One part of crystal violet was dissolved in 400 parts of glycerol andthe solution was added to 1600 parts of deflbrinated blood virusobtained from a hog sick with cholera. The resulting mixture wasincubated at about 375 C. for an interval of time suflicient to destroythe disease-producing power of the virus. About a two-week period ofincubation is ordinarily allowed, although potent, sterile hog choleravaccines have been obtained under this process in periods as short assix days. a

The vaccine thus produced has in all cases been found to be sterile-andof suitable potency for its purpose. It may be stored at long intervalswithout deterioration and may be administered without danger orcontamination when used un der field conditions, since the antisepticproperties are suflicient to destroy at least all ordinary organismswhich may be inadvertently introduced.

- of blood virus, crystalviolet and glycerol and the temperature andtime of incubation being such that a sterile vaccine results.

2. A process of preparing sterile vaccine for immunizing swine againsthog cholera, comprising mixing blood virus obtained from hogs sick withcholera with a solution of crystal violet in in the proportion 01' aboutfrom 15 percent to 25 percent or the solution to about from 85 percentto '75 percent of the blood virus, and incubating the mixture at suchtemperature and over such interval of time that the disease-producingprinciples are destroyed without destroying the protective properties.

3. A process oi preparing sterile vaccine for immunizing swine'againsthog cholera, comprising mixed blood virus obtained from hogs sick withcholera with 'a solution 01 crystal violet in glycerol in aconcentration of about 0.25 percent, in the proportion of about 20percent of the solution to about 80 percent of the blood virus, andincubating the mixture at such temperature and over such interval 01'time that the disease-producing principles are destroyed withoutdestroying the protective properties. 7

- FRANK W. TlLLEY.

